Computer users employ writable and rewritable optical discs for a variety of different purposes. They may save programs or data to the discs such as for archival or distribution purposes. In the case of CD-type discs, users may make music CDs that can be played in audio CD players, or save music data files to the CDs, such as MP3 files, that can be played in special-purpose CD players. In the case of DVD-type discs, users have greater storage capacity than with the CD-type discs and may be able to make video DVDs that can be played in stand-alone DVD players.
Optical discs include a data side and a label side. The data side is where the programs and the data are written, and the label side allows the user to label the optical disc. However, labeling can be a laborious or even an expensive process that results in an unprofessional looking label. For instance, markers can be used to write on the label side of optical discs, but the results look unprofessional. Special pre-cut labels can also be printed with inkjet or other printers, but this is a labor-intensive process, as the labels must be carefully aligned on the discs and, if the labels are not properly placed on the disc, the label may even damage the disk drive.
Some labeling mechanisms label the disc using horizontal sweeps with either the labeling mechanism or the disc being incrementally moved between sweeps. Such mechanisms are typically separate from, or add significant incremental cost to, the optical disc drive that writes the data or programs to the disc.
Other radially oriented labeling mechanisms rotate and mark the circularly shaped disc at different linear velocities depending on the distance of a mark from the center of rotation of the disc. For example, when the circularly shaped disc rotates at a constant velocity, the center of the disc rotates at a slower speed than the outer edge of the disc.
The difference in linear velocities often results in varying tangential labeling resolutions at different distances from the center of rotation, and thus distortion of the resulting labeled image.
In some radially oriented labeling mechanisms, the source label image is manipulated or converted from a rectangular coordinate pattern to an angular coordinate system. The particular method used to convert the rectangular coordinate pattern to an angular coordinate system can also introduce distortions in the label. Existing disc labeling systems have converted the source label image from rectangular coordinates to polar coordinates, consisting of a distance from the center of rotation of the disc and an angle of rotation. However, a fixed precision polar coordinate system causes the marking resolution to decrease as the distance from the center of rotation increases.